Added verification digit for Colombian NIT.

Author: Igor Támara

localflavor/co/forms.py

@@ -1,6 +1,10 @@
 """Colombian-specific form helpers."""
 
 from django.forms.fields import Select
+from django.forms import ValidationError
+from django.forms.fields import RegexField
+from django.core.validators import EMPTY_VALUES
+from django.utils.translation import ugettext_lazy as _
 
 from .co_departments import DEPARTMENT_CHOICES
 
@@ -10,3 +14,62 @@ class CODepartmentSelect(Select):
 
     def __init__(self, attrs=None):
         super(CODepartmentSelect, self).__init__(attrs, choices=DEPARTMENT_CHOICES)
+
+
+class RUTField(RegexField):
+    """
+    This field validates a NIT (NUmero de IdentificaciOn Tributaria). A
+    NIT is of the form XXXXXXXXXX-V. The last digit is a check digit. Applies
+    to people and companies.
+
+    More info:
+    http://es.wikipedia.org/wiki/N%C3%BAmero_de_Identificaci%C3%B3n_Tributaria
+    """
+    default_error_messages = {
+        'invalid': _('Enter a valid RUT in XXXXXXXXXXX-Y or XXXXXXXXXXXY format.'),
+        'checksum': _('Invalid RUT.'),
+    }
+
+    PRIME_PLACES = [3, 7, 13, 17, 19, 23, 29, 37, 41, 43, 47, 53, 59, 67, 71]
+
+    def __init__(self, max_length=None, min_length=None, *args, **kwargs):
+        super(RUTField, self).__init__(
+            r'^\d{5,12}-?\d$',
+            max_length,
+            min_length,
+            *args,
+            **kwargs
+        )
+
+    def clean(self, value):
+        """
+        Value can be either a string in the format XXXXXXXXXX-Y or
+        XXXXXXXXXXY.
+        """
+        value = super(RUTField, self).clean(value)
+        if value in EMPTY_VALUES:
+            return ''
+        value, cd = self._canon(value)
+        if self._calc_cd(value) != cd:
+            raise ValidationError(self.error_messages['checksum'])
+        return self._format(value, cd)
+
+    def _canon(self, nit):
+        nit = nit.replace('-', '')
+        return nit[:-1], nit[-1]
+
+    def _calc_cd(self, nit):
+        # Calculation code based on:
+        # http://es.wikipedia.org/wiki/N%C3%BAmero_de_Identificaci%C3%B3n_Tributaria
+        tmp = sum([
+            self.PRIME_PLACES[idx] * int(value)
+            for idx, value in enumerate(reversed(nit))
+        ]) % 11
+        if tmp > 1:
+            dv = 11 - tmp
+        else:
+            dv = 0
+        return str(dv)
+
+    def _format(self, nit, check_digit):
+        return '{0}-{1}'.format(nit, check_digit)

tests/test_co.py

@@ -3,6 +3,7 @@
 from django.test import SimpleTestCase
 
 from localflavor.co.forms import CODepartmentSelect
+from localflavor.co.forms import RUTField
 
 
 class COLocalFlavorTests(SimpleTestCase):
@@ -44,3 +45,25 @@ def test_CODepartmentSelect(self):
 <option value="VID">Vichada</option>
 </select>"""
         self.assertHTMLEqual(d.render('department', 'COR'), out)
+
+    def test_ARCUITField(self):
+        error_format = ['Enter a valid RUT in XXXXXXXXXXX-Y or XXXXXXXXXXXY format.']
+        error_invalid = ['Invalid RUT.']
+        valid = {
+            '37547837-0': '37547837-0',
+            '900227140-3': '900227140-3',
+            '79626331-8': '79626331-8',
+            '375478370': '37547837-0',
+            '796273731': '79627373-1',
+            '9002271403': '900227140-3',
+        }
+        invalid = {
+            '2-375478370-9': error_format,
+            '20-10123456-': error_format,
+            '3-375478370': error_format,
+            '375478370-': error_format,
+            '37547837-5': error_invalid,
+            '37547837-2': error_invalid,
+            '9002271401': error_invalid,
+        }
+        self.assertFieldOutput(RUTField, valid, invalid)